Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery pack having a plurality of battery cells electrically connected to each other because high power and large capacity are necessary for the middle or large-sized devices.
Preferably, the middle or large-sized battery pack is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery pack. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing cost of the pouch-shaped battery is low, and it is easy to modify the shape of the pouch-shaped battery.
In order for the middle or large-sized battery pack to provide power and capacity required by a predetermined apparatus or device, it is necessary for the middle or large-sized battery pack to be configured to have a structure in which a plurality of battery cells is electrically connected in series or in series and parallel to each other, and the battery cells are stable against external force.
Meanwhile, a conventional battery pack is configured to have a structure in which an appropriate number of battery modules are fixed to a base plate, an end plate, and a support bar to secure dynamic stability.
In the battery pack with the above-stated construction, however, there is a space restriction when the battery modules are mounted. Also, when a large number of battery modules are used to constitute the battery pack, overall structural stability of the battery pack is lowered.
Also, the conventional battery pack is configured such that the battery modules are fixed to the base plate using bolts or nuts to prevent upward and downward movement of the battery module, and the battery modules are fixed by the end plate and the support bar in the longitudinal direction, thereby secure dynamic stability.
In the battery pack with the above-stated construction, however, the battery modules are fixed to the base plate using bolts or nuts with the result that an assembly process is complex. Also, it is necessary to secure a space for the fastening members with the result that there is a space restriction and weight restriction of the fastening members.
Consequently, there is a high necessity for a battery pack having a compact structure that is capable of solving the above-mentioned problems.